The present invention relates generally to uplink data scheduling in a mobile communication system, and in particular, to a method and apparatus for adjusting a rate therein of uplink data.
Mobile communication systems have been developed with an aim to provide communication while guaranteeing mobility of users thereof. The mobile communication technology has been evolving to support not only the voice communication services but also the high-speed data communication services.
Recently, standardization work on Long Term Evolution (LTE), one of a plurality of next-generation mobile communication systems, is being conducted in a 3rd Generation Partnership Project (3GPP). The LTE system is a technology for implementing high-speed packet-based communication at a rate of a maximum of about 100 Mbps, which is higher than that of the currently available data rate, aiming at its commercialization about 2010. To this end, several communication schemes are now under consideration, and they include a scheme of simplifying, for example, a configuration of the network, i.e., reducing the number of nodes located in the communication path, and a scheme of maximally approximating radio protocols to wireless channels.
Meanwhile, data service is determined according to the amount of desired transmission data, channel conditions, and allocable resources. A scheduler of the mobile communication system allocates transmission resources taking into account the amount of desired transmission data, channel conditions, and available wireless resources. Even the LTE system is expected to include a scheduler that will manage wireless resources in the same manner and the scheduler can be included in a Node B.
The mobile communication system is divided into downlink transmission and uplink transmission according to data transmission direction. The downlink transmission includes a transmission direction from a Node B to a User Equipment (UE), while the uplink transmission includes a transmission direction from a UE to a Node B. Regarding allocation of downlink wireless resources, the Node B can correctly detect channel conditions, the amount of resources, and the amount of transmission data. Therefore, the scheduler of the Node B can smoothly perform downlink scheduling. However, regarding allocation of uplink wireless resources, since the scheduler cannot correctly detect buffer status of UEs, it may have difficulty in performing correct scheduling for uplink transmission.
It is obvious that the mobile communication system needs a scheme for more accurate uplink scheduling. In this context, to smoothly perform uplink scheduling, a High Speed Uplink Packet Access (HSUPA)-based mobile communication system uses a scheme in which a UE transmits 1-bit information, called a ‘happy bit’, to a Node B, thereby adjusting its uplink data rate.
The ‘happy bit’, as used herein, means information indicating whether or not the UE is satisfied with the current data rate, and the scheduler of the Node B determines whether to allocate additional resources to the UE depending on the ‘happy bit’. Particularly, in the HSUPA system, the ‘happy bit’ is transmitted over a separate uplink control channel associated with an uplink data transmission channel, and it is transmitted over an uplink control channel every time the UE transmits data on the uplink.
Even in the LTE system, UE's providing the ‘happy bit’ to the Node B would be advantageous to a scheduling operation. However, the current LTE system, unlike the HSUPA system, has no separate uplink control channel associated with the data transmission channel. In other words, the LTE system cannot transmit the ‘happy bit’, i.e., satisfaction/non-satisfaction of the uplink rate, using an uplink control channel, like the HSUPA system.
Therefore, there is a need for a detailed scheme regarding how to transmit and check satisfaction/non-satisfaction of the uplink data rate in the LTE system. That is, there is a need for a detailed scenario regarding how to perform uplink data scheduling in the LTE system.